A suicide blast killed at least 21 people in Afghanistan’s northern province of Kunduz on Sunday, capping off one of the country’s most violent weekends in years.

The Afghan interior ministry said all those killed on Saturday evening were civilians, although local officials called them anti-Taliban militiamen. Ten other people were wounded in the explosion, the ministry said.

"The incident took place (when) a suicide bomber detonated his suicide vest," the interior ministry said, strongly condemning the "heinous act".

The Taliban claimed responsibility for the attack, which comes after a string of bombings that began in Kabul on Friday, killing at least 51 and wounding hundreds more.

The attacks in the capital were the first major militant assaults since the announcement of Taliban leader Mullah Omar's death, dimming hopes that the Islamist group might be weakened by a leadership struggle.

Offices flattened

The recent wave of violence began when a truck bomb exploded in a heavily populated district of Kabul on Friday and included an hours-long battle at a base used by US special forces.

On Saturday, NATO-led coalition forces confirmed that one international force member and eight Afghan contractors had been killed in the assault on the base.

The blast outside Camp Integrity was powerful enough to flatten offices inside, wounding occupants who were airlifted by helicopter to military hospitals.

“There was a big explosion at the gate ... (The gunfire) sounded like it came from two different sides,” a special forces member, who was wounded when his office collapsed, told Reuters.

The brazen operation was followed by a suicide bombing at a police academy that killed and wounded more than 40 people, according to Afghan officials.

The UN mission in Afghanistan said Friday was the most violent day since it began recording civilian casualties in 2009, with 355 civilians killed or injured.

No peace

The bloodshed was a reminder of the difficulty of reviving a stalled peace process, and of the firepower the insurgency continues to wield.

Divisions have broken out within the Taliban high command following the appointment of Mullah Akhtar Mansour as leader.

Previously seen as open to reviving peace talks, he has since pledged to press on with the insurgency, which has killed or wounded thousands this year.

The conflict between the Western-backed government and the Taliban has intensified since the NATO combat mission ended last year, but Afghan security forces and civilians have borne the brunt of the violence.